The invention provides a process for the preparation of L-amino acids, in particular L-lysine, by using coryneform bacteria in which the pfkA gene coding for 6-phosphofructokinase and/or the pfkB gene coding for 1-phosphofructokinase are/is attenuated. All references cited herein are expressly incorporated by reference. Incorporation by reference is also designated by the term “I.B.R.” following any citation.
L-amino acids, in particular L-lysine, find application in human medicine and in the pharmaceutical industry, in the food industry and, quite especially, in animal nutrition.
It is known that amino acids are prepared by fermentation of strains of coryneform bacteria, in particular Corynebacterium glutamicum. On account of its great importance, work on improving the production process is constantly in progress. Improvements to the process may concern measures pertaining to fermentation technology, such as, for example, stirring and provision with oxygen, or the composition of the nutrient media, such as, for example, the sugar concentration during fermentation, or the reprocessing into product-form by, for example, ion-exchange chromatography, or the intrinsic output properties of the micro-organism itself.
With a view to improving the output properties of these micro-organisms, methods of mutagenesis, selection and mutant selection are adopted. In this way, strains are obtained that are resistant to antimetabolites such as, for example, the lysine analogue S-(2-aminoethyl)cysteine or that are auxotrophic in respect of metabolites of regulatory significance and that produce L-amino acids.
Methods pertaining to recombinant DNA technology have also been employed for a number of years for the improvement of strains of Corynebacterium glutamicum producing L-amino acid, by individual amino-acid-biosynthesis genes being amplified and by the effect on the production of L-amino acid being investigated.
The invention provides improved processes for the fermentative preparation of L-amino acids, in particular L-lysine, by using coryneform bacteria.